Groundwater flow in heterogeneous media containing aquitards

The rocks of the subsurface, because of the geological processes which they undergo have undergone since the beginning of their formation , mainly represent heterogeneous groundwater basins, from a hydrogeologic point of view. The field activities carried out in such kind of system in Longano (Isernia, Southern Italy) allowed to refine their hydrogeologic functioning. In the case of systems consisting principally formations with low permeability, even when, at the basin scale, they significantly impede groundwater flow, due to their heterogeneity the dynamics observed within them appear heavily controlled by the functioning of the adjacent hydrostructure. In greater detail, because of the heterogeneity of the system (highly permeable horizons and the network of structural discontinuities like faults and fractures), the groundwater flow dynamics are strictly controlled by the behavior of the nearby highly permeable carbonate systems. With respect to highly receptive hydrogeologic systems, due to the heterogeneity of the rock masses, during recharge and discharge, non-uniform rebalancing of the hydraulic heads can occur. This leads to the activation of further modifications of the field potential, which could transmit downgradient, due to the lesser permeable portions of the media, also with a delay. However, because of the high receptivity of the entire aquifer system with respect to the rainfall, the overlapping of the effects yielded by the variations of the groundwater flow pattern are able to significantly regulate the dynamic functioning of the system, counteracting or enhancing the general raising (or lowering) of the water table. On the whole, the results of these studies highlight the important role played on the groundwater basins by the distribution of permeability, which can make the flow dynamics more complex than usually believed. the need to refine their knowledge through experimental activities arises from the important implications of such dynamics on both the usage and the protection of groundwater resources.